4ao M. de luc’s Barometrical Obfervations on 
Having made thefe experiments within the mines, I 
was defirous of making fome in the open air, which I 
had foon a very agreeable opportunity of doing; for 
having communicated my defire to Mr. reden, he and 
Mr. rausch, the principal of the fubterraneous geome- 
ters, were fo good as to be of the party. The latter had 
had occafion to determine moft accurately the height of 
two external points of the Hartz, relatively to the mines 
of Claufthal and Zellerfeld. Nothing more, therefore, 
was required but to obferve the Barometer at the entry 
of a certain mine, which was a fixed point, and to 
obferve it again at thefe two external points; one of 
which was about 3000 toifes horizontal diftance, beyond 
a fmall hill; and the other, 5000 toifes off, entirely 
without the Hartz. 
We 
Apres avoir fait ces experiences dans Tinterieur des mines, je defirois beaucoup 
d’en faire aufti en plein air. L’ayant temoigne a M. i>e reden, il m’en fournit 
un moyen tres agreable ; car lui meme, et M. rausch chef des geometres fou- 
terrains, furent de la partie.. Ce dernier avoit eu befoin, a Toccafion d’un projet 
de galerie d’ecoulement, de determiner avec la pl-us grande exa&itude la hauteur 
de deux points exterieurs au Hartz, relativement aux mines de Claufthal et de 
Zellerfeld. II ne s’agiftoit done que de faire l’obfervation du Barometre a l’entree 
d’une certaine mine, qui etoit un point fixe ; et de Taller faire enfuite a ces deux 
points exterieurs; dont Tun etoit a environ 3000 toifes de diftance horizontal, 
au de la d’une eolline, et l’autre a 5000, toifes, entierement au dehors du 
Ha.tz, 
5 
Nous 
